How can I best prepare for building Windows Phone 8 Apps

Question

I'm interested in learning to develop for Windows Phone down the road a bit, and am mostly interested in developing Metro Apps for the Windows Phone. It seems like there is some basic info for Metro development now, but no guidance on what will be relevant when Windows Phone 8 releases. There seem to be two potential strategies:

1) Start coding for Mango/WP7.5 and then later attempt to convert the experience for use with WP8. I guess this would involve learning Silverlight for applications (as opposed to XNA for games)?

2) Write Windows 8 Metro apps now with the dev preview. This experience seems less likely to be deprecated but it also seems harder to test in a real world fashion.

I'd normally lean towards option 1, but there are a few downsides with that route imo. First, I'd read elsewhere that Silverlight 5 was the last Silverlight release. I'm not completely clear on how much Silverlight experience will be useful for future iterations on their phone OS. Also, one thing I find interesting is the improved async/await setup and my understanding is that WP7 still relies heavily on callbacks for async operations.

I'm pretty unfamiliar with Silverlight/WP7/etc so please be gentle if there are some flagrant misunderstandings on my part. Thanks!